If you have access to your router/firewall, please try forwarding ports and adding a firewall exception as per the instructions in the readme.txt (located GameCrysis2/Support/Readme.txt)!
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Hi Cry-Adam,
I forwared port 64100 from extern on UDP to my maschine, but that didn't work.
I ignored the rest of the readme.txt because this is way too much to play a game.
Despite that I closed the port again and it works anyway with a disconnect inbetween the login and the click on multiplayer. I hope that helps.